There are many situations in which it is desirable to remove unwanted tissue from a patient. Uterine fibroids and uterine polyps are two examples of such unwanted tissue. Uterine fibroids are well-defined, non-cancerous tumors that are commonly found in the smooth muscle layer of the uterus. Uterine polyps are masses that are commonly found extending from the inner lining of the uterus. In many instances, uterine fibroids and uterine polyps can grow to be several centimeters in diameter and may cause, for example, menorrhagia (prolonged or heavy menstrual bleeding), pelvic pressure or pain, and reproductive dysfunction. It is believed that uterine fibroids occur in a substantial percentage of the female population, perhaps in 20 to 40 percent of all women, and that uterine polyps occur in up to 10 percent of all women.
One type of treatment for uterine fibroids and uterine polyps is hysteroscopic resection. Hysteroscopic resection typically involves inserting a hysteroscope into the uterus through the vagina, i.e., transcervically, and then cutting away the unwanted tissue from the uterus using a device delivered to the unwanted tissue by the hysteroscope. Hysteroscopic resections typically fall into one of two varieties. In one variety, an electrocautery device in the form of a loop-shaped cutting wire is fixedly mounted on the distal end of the hysteroscope—the combination of the hysteroscope and the electrocautery device typically referred to as a resectoscope. The transmission of electrical current to the uterus with a resectoscope is typically monopolar, and the circuit is completed by a conductive path to the power unit for the device through a conductive pad applied to the patient's skin. In this manner, tissue is removed by contacting the loop with the part of the uterus wall of interest. Examples of such devices are disclosed, for example, in U.S. Pat. No. 5,906,615, which is incorporated herein by reference.
In another variety of hysteroscopic resection, an electromechanical cutter is inserted through a working channel in the hysteroscope. The electromechanical cutter, sometimes referred to as a morcellator, is a motor-driven instrument that typically includes (i) a tubular member having an end or window through which tissue may enter and (ii) a cutting instrument positioned within the tubular member for cutting the tissue that has entered the tubular member. Suction or surgical grasping instruments are employed to draw tissue into the tubular member, which includes a cutting instrument that is used to cut the tissue into smaller pieces or “morcels.” Examples of the electromechanical cutter variety of hysteroscopic resection are disclosed in, for example, U.S. Pat. Nos. 7,226,459; 6,032,673; 5,730,752; U.S. Publication No. 2012/0172889 A1; U.S. Publication No. US 2009/0270898 A1; U.S. Publication No. 2009/0270812 A1; U.S. Publication No. US 2006/0047185 A1; and PCT International Publication No. WO 99/11184; each of which is incorporated herein by reference. In other procedures to treat uterine fibroids and uterine polyps, laparoscopic morcellators are employed in a laparoscopic (rather than hysteroscopic) procedure. Examples of laparoscopic morcellators are described in U.S. Pat. Nos. 5,520,634 and 6,039,748, each of which is incorporated herein by reference.
It is generally desired to minimize the duration of surgical procedures such as hysterectomies. The tissue removal rates achievable with known morcellators and resection devices may be limited, thus resulting in surgical procedure durations that are longer than desired. Such devices may also be characterized by exposed cutting blades or surfaces, thus risking unintended tissue removal or damage. There is a need for surgical resection devices that provide a high rate of tissue removal while also protecting tissues that are not intended to be removed during a surgical procedure.